Upgrade your ssh server and use better encryption, you should have stopped using RSA about 15 years ago. On a different note, you deservedly will only be receiving mediocre applications since anyone technical enough will pass on after seeing this mess.
just to clarify, I don't think "oversized image" was a mistake on author's part, but a deliberate attempt to inflate book size, hence the rest of my sentence
You wrote a notebook, not a book. Also your example pages have oversized images and still you only have 130 pages of content, yet you are charging an extreme amount for it.
It is a feature. As a frequent user, I would rather have it on plain HTTP as well. Aside from the performance benefit, it also helps if people monitoring my internet traffic (my ISP, NSA, Putin, Zuck etc.) reads Paul Graham and they may get enlightened. May not seem much but it is actually one of the few steps humanity is taking towards world peace.